Method of cylinder etching and machine therefor



Sept. 19, 1950 2,523,018

METHOD OF CYLINDER ETCHING AND MACHINE THEREFOR Filed Dec. 12 1946 C. L. HENDERSON 5 Sheets-Sheet 1 5 Sheets-Sheet 2 l =L l:- 1 ll lllll l C. L. HENDERSON METHOD OF CYLINDER ETCHING AND MACHINE THEREFOR I 1 mmvroa.

(ha/5 i finale/507a Sept. 19, 1950 Filed Dec. 12, 1946 P 1950' E c. HENDERSON 1 2,523,018

I METHOD OF CYLINDER ETCHING AND MACHINE THEREFOR Filed Dec. 12, 1946 s Sheets-Sheet 4 p 19, 1959 i c. L. HENDERSON v 2,523,018

METHOD OF CYLINDER ETCHING AND MACHINE THEREFOR Filed D60. 12, 1946 5 Sheets-Sheet 5 I N VEN TOR.

Patented 19, p 1950 UNITED; STATES PATENT .QFFICE METHOD OF CYLINDER ETCHINGAND MACHINE THEREFOR Charles L. Henderson, Appleton, Wis., assignor" to Paper Patents Company, a corporation of i Wisconsin Application December- 12, 1946, Serial No. 715,893 I 6 Claims.

; M intaglio or reiiefprintin'g cylinders.

In intaglio printing the printing surface ordinarily comprises a smooth, metallic surface, usually of copper, having etched therein, symmetrically arranged ink-receiving recesses of very small area. The-ink recesses throughout the printing surface are'separated by line-like, unietched lands, which serve to support the doctor or scraper blade used for removing excess ink from the printingsurface during the actual printing operation. l l

The quality of the printing surface is to a large extent dependent upon the. obtaining of a uniformly etched surface during the etching operation. Various methods and procedures have been developed for etching printingsurfaces. The etching machin and the method disclosed in my a prior Patent 2,360,676 make possible continuous, -mecl1anical etching procedures, which are importantsteps forward in the art.

The present invention is 'an improvement on i the apparatus and method of my prior patent, and has for its principal object the provision of a machine and method whereby theprogress of the etching on the printing surface can be closely controlled so that a more uniformly etched surface, having very accurate tonal quality, will be produced. Other objects and advantages of the invention will be made clear by reference to the accompanying drawings and the following description of one preferred embodiment thereof.

In the drawings, i l

\ Fig. 1 i; an end elevational view, partially in section, of an etching machine constructed in accordancewith the present invention;

, Fig. 2 is a fragmentary side elevational view, partially in section, of the etching machine illustrated in Fig. 1;' l

Fig. 3 is a sectional view taken on line 33 I of Fig. 2; h i l Fig. 4 is an enlarged, fragmentary, sectional view of the improved'etching fluid control means of the present invention; I

Fig. 5 is a sectional view generally similar to Fig. 3 showin a modified form of the apparatus of the present invention; i

Fig. 6 is a view taken on line 66 of Fig. 5; Fig. '7 is a fragmentary, perspective view illustrating one means of adapting the apparatus of the other figures of the drawings for use in connection with short printing cylinders, and;

Fig. 8 is a-sectionalview taken on line 8-8 in Fig. 4.

The etching machineillustrated in the drawing is designed particularly for etching printing cylinders of standard sizes, and comprises generally a. relatively heavy frame structure; a pair of bearings, adjustably supported on columns, for rotatably supporting the printing cylinder which is to be etched; means for rotating the printing cylinder; a container for the acid or other etching" fluid; means for applying said fluid to the printing cylinder; and means for controlling the area on which the etching fluid acts and, also, the time of contact between the etching fluid and the surface being etched. The means for controlling the action of the etching fluid are particularly important features of the improved machine. In effecting this control, barriers of pressure air are utilized to limit the area of'the cylinder subjected to the etching fluid, and this same air barrier is also used to doctor off excess etching fluid. A water spray is used to check the action of the etching fluid at times when the surface of the cylinder is not in contact with the fluid. Thus, the need for doctor blades or rollers which mechanically contact the surface to be etched is eliminated, and the surface being etched' comes in contact with only etching fluid, air and wash water.-

The frame structure illustrated, includes a heavy rectangular frame Ii which is supported upon upright members IS. The frame members I I and I3 are desirably of relatively heavy structural steel and are covered with an acid-resisting coatingat all points wher there is possibility of contact with the etching fluid. Suitable platforms are included on the frame to provide support for the driving motors and other associated apparatus.

An etching fluid or acid tank l5 extends longitudinally to the frame and is supported at the ends and the various points along its length as necessary to provide a, rigid structure. The acid tank I 5 is desirably shaped as is illustrated in the drawings, and has a-longitudinally extending shell portion l6 having an arcuate section, I! extending for approximately 260 around the bottom of the shell I 6 and relatively straight side portions i9 which converge to form a longitudinally extending throat 2| having an opening about four inches wide. The ends 23 of the container 1 5 are plane surfaces and are desirably 3 inner portion of the tank l5 and the acid inlet 25 should be covered by a suitable acid-resisting material as, for example, a A; inch coating of pure black gum rubber or a suitable acid-resisting paint or cement.

A large circular portion, indicated at 22, is cut out of each of the end sections 23 to provide a means of access to the interior of the acid tank l5 and means for removing or servicing an impeller member 29 which is to be hereinafter described in detail. The openings resulting from the cut-out portions 22 are sealed by removable plate members 3| which contain bearings 33 for rotatably supporting the shaft for the impeller 29. A seal between the plate members 3| and,

the end sections 23 of the acid container I5 is provided by inserting a rubber gasket 35 between the plate members 3| and the end sections 23 of the acid tank 15. The gasket 35 acts as an extension of the rubber or other acid proof coating provided on the inner surface of the acid container and thus insures that the metal will not be exposed to the action of the etching fluid.

The acid, or other etching fluid, indicated in Fig. 3 at 21, is atomized and applied to the surface which is to be etched by means of a rotatable impeller member 29 which is desirably provided with a deflector 31. The deflector 31, if used, may comprise a longitudinally extending arcuate member (about 90) which isattached to the bearing members 33 by means of brackets 34 at each end of the acid tank l5, in a position adapted to direct the acid thrown from the impeller 29 against the surface to be etched. The deflector 31 may be fabricated from steel and coated with a suitable acid-resisting material, or it may be fabricated from acid-resisting plastic or the like. The impeller 29 of the apparatus illustrated in the drawings comprises a series of paddle members 39 made from an acid-resisting plastic such as that sold under the trade name of Lucite, or some other acid-resisting material. The paddle members 3| are affixed to a suitable rotatable shaft 4|; one end of the shaft 4| extends through an opening in one end of the acid tank l5 for connection to a motor 46 or other rotating means, as illustrated in Fig. 2.

The impeller 29 is supported for free, high speed rotation within the acid container |5 by suitable bearings 33 (Fig. 2). The impeller shaft 4| has an enlarged baille portion.45, intermediate the ends of the paddle members 39 and the end of the shaft 4|, which is adapted to cooperate with a cone-shaped bearing seal 34a through which a stream of pressure air is passed. The bearings 33 are thus protected from the corrosive action of the etching fiuid by the stream of pressure air which sweeps all foreign materials out of the protecting cone 34.

The motor 46 which is used for rotating the impeller 29 is supported on a bracket 41 affixed to the frame upright l3, and is connected to the impeller shaft 4| by a belt 49 and suitable pulleys 5| and 53. A constantspeed motor with variable speed pulleys is desirable, so that the atomization of the acid may be closely controlled. The impeller 29 should be rotated at relatively high speed in order to accomplish good atomization and an even distribution of the etching fluid along the surface which is to be etched. Impeller speeds upwards of about 1200 R. P. M. have been found to be satisfactory.

The acid tank I5 is surrounded by an air jacket 55 fabricated from sheet material. The air jacket 55 is shaped to conform with the shape of the acid tank l5, and is large enough to allow for the free circulation of air around the outside of the acid tank as is shown by the arrows 51. air inlet 59 to the jacket 55 is conveniently provided at the bottom portion of the jacket 55 and a heavy duty, centrifugal blower 5| is supported adjacent the air inlet 59 for supplying the needed pressure air.' An outlet pipe 63 is provided at each end of the air jacket to connect the conical bearing seal 34, before described, with a source of pressure air. The blower 6| is adapted to be powered by a motor 65 and both the motor. 65 and-the blower 5| are supported on a suitable frame 51.

Two longitudinally extending air nozzles or slots 69 are formed between the outside surface of the acid tank |5 and theinner surface of the air jacket 55 by means of longitudinally extending structural members 1| and 13 shaped as shown in the drawings (Figs. 3 and 4). The members 1| and 13 are joined by a series of counter-sunk machine screws 15 which are adapted to engage threaded holes in the inner member 13. The members 1| and 13 are maintained in their relative positions by means of adjusting screws 11 which are threaded into the outer member 1| and which have extensions adapted to press upon the upper walls IQ, of the acid container l5, and on the inner structural member 13.

Adjusting the pairs of screws 15 and 11 thus provides a convenient means for carefully adjusting the width of the air nozzles or slots 59. The inner members 13 are attachedto the ends of. the acid tank I5 and to the frame H by means of machine screws 19 and, thus, provide additional longitudinal stiffening of the structure. The inner members 13 are shaped as shown in the drawings so as to provide a throat 8| having parallel walls 83 and 85 for guiding the etching fluid spray against the surface to be etched as indicated by the arrow 81 in Fig. 4.

A water pipeline 89 is supported on the frame H by brackets 9| and extends longitudinally in close proximity to-the air slot 69. The water pipeline 89 has a continuous slot 93 on the inner side adapted to direct water from the pipeline 83 onto the surface of the cylinder 95, thus halting the etching action on all sections of the cylinder not in immediate contact with the atomized etching fiuid. Drain trays 91 are provided on each side of the structure between the air jacket 55 and the outer frame members The trays 91 may be fabricated from sheet metal and are, if provided with a drain outlet 99, connected to a sewer or other disposal means. The outerlongitudinal air slot members 1| are shaped with an added flanged portion 0| adapted to provide a leakproof bond between the member 1| and the drain trays 91 (Fig. 4).

In order to control the. level of the etching fluid 21 in the acid tank l5, an adjustable height, filling-container I03 is provided. This is removably fastened to a bracket 14 on the frame l3 and is connected to the inlet 25 of the acid container l5 by means of a gum rubber or other acid-resisting, flexible hose I06. All the surfaces of the filling-container I03 are covered with an acid-resisting coating. It is advantageous if one of the sides of the container I03 is formed into a spout or guide )8 so that the etching solution may be conveniently poured from the filling container I03 when it is desired to drain the acid from the main acid tank l5.

As printing cylinders vary considerably in length and in diameter, a cylinder etching ma- The chine should include means for accommodating cylinders of varying dimensions as is shown in Fig. 3 as 95 and 95a. In the particular machine shown in the drawings, this means includes an adjustable bearing support structure for the cylinder 95 which is to be etched. This structure includes two screw jack members I95 actuated by knurled knobs II". The jacks I95 are rigidly attached at each end of the frame I I. An extensible portion I99 of each jack I05 terminates in a yoke section I II adapted to support ball bearing rings II 3 which are slipped over the ends of the printing cylinder shaft I I5 to facilitate rotatable movement The adjustment of thedistance between the surface of the cylinder being etched V and the outlet of the air slots 69 is a most important adjustment in the successful operation of the etching machine. For this reason, the jack members I95, desirably have low-pitch threads so that the gap.between air slot 69 and the cylinder.

is locked in by means of a screw locking means.

III. A pulley I23 on the motor drive shaft is operatively connected to a pulley I which is adapted to fit on the cylinder shaft I I 5 by means of the belt H9. During the actual etching operation, it is desirable that the printing cylinder 95 which is to be etched'should be rotated at a relatively low speed. Tests indicate the linear speed of the surface being etched should be within the range of from about 25 to feet per minute. For

. I5 is high enough to allow the impeller blades 39 to dip into the acid about inch at the lowest postion in their are of travel. The cylinder 95 which hasthe ball bearing rings H3 in place on diate the opening of the air slot 99 and the cylinder 95 effectively-confines the acid spray to the areas of the cylinder directly above the slot 9| in the acid tank I5. The air also keeps the water spray from entering the acid tank I5 and diluting the acid. In operation, one section of the ill) cylinder 95 passes through the acid solution spray, the acid solution is doctored off by the air blast from the adjacent'slot, the surface is then washed with water, and the cylinder 95 iotates around to the second air slot where it may be partially dried by the blast and again enters the acid spray. The excess wash water runs down the two drain trays 9I and out the drain pipe provided.

When etching relatively short cylinders, it will be found desirable to partially cover both ends of the impeller housing with an acid-resisting removable bafiie I21 as illustrated in Fig. "I. The baiiie I2! is desirably a plate of Lucite or other acid resisting plastic which is held in position by means of' cross members I29 and bolt andwing nut assembly I3I. This arrangement conflnes the discharge of the etching fluid to the length of the cylinder which is to be etched. The wash water is confined along an equivalent length of the water pipeline 89 by means of a removable sleeve member I33 which is held in pgsligion by a strap locking meansas shown a 5. I

The modified form of the apparatus illustrated in Figs. 5 and 6 is essentially similar to the machine which has been described in the ing, with this one important exception:

In the modified apparatus, the etching fluid is directed against the surface to be etchedby means of a liquid jet atomizing structure I31 which is operated by a plurality of spaced air jets. The atomizing structure I31 includes a pair of complementary, machined plate members I39 which are designed so as to provide a plurality of regularly spaced atomizing 'jet chamforego- -bers Ill which open into wedge-shaped throats its shaft" H5, is cradled in the yokes III .pro- I vidd for thebearings I I3 on the adjustable supporting members I09. The height of the yokes III is adjusted so that the gap between theair slot 59 and the surface of the cylinder 95 is from about to A; of an inch. The cylinder driving motor 43 is energized and the speed of rotation is adjusted to conform with the etching conditions required. The air blower 6| is started and then the spray from the water pipeline 89 is turnedon. The impeller 29 is energized and its speed is adjusted to provide the most desirable atomization of the etching solution 21. etching is continued until the ink receiving recesses havebeen etched to the required depth and then the impeller 29 is stopped and the cylinder is rotatedin the water spray and air blast. After the surface of the cylinder 95 is thoroughly washed, the water from the manifold 89 may be It has been found that a pressure differential of from about 1 to 5 pounds per square inch The I43 wherein are disposed deflector members I45 for dividing and directing the atomized stream so as to assure full coverage at the open upper end'of the throat. The complementary plate members I39 are bolted together and are held inplace within the acid tank I5a by means of cleats or the like (not shown). A jet tube I49 is provided in each of the atomizing chambers HI and this tube is connected to a suitable source of pressure air through a conduit I5I. Particularly satisfactory results have been obtained when using a jet tube having an orifice about inch in diameter and an'air pressure of about 15 pounds per square inch gauge. The air slots 69a, the outer'air jacket 55a, the water pipeline 89a, and the vertically adjustable support means for the cylinderwhich is to be etched are exactly the same in this apparatus as in the previously described structure.

Tests have shown that the etching apparatus which has been described in the foregoing, is capable of producing gravure cylinders of particularly high quality. etching fluid and the rotating cylinder is closely controlled by the doctoring action of the air blasts and by the dilution of the etching solution by the wash\water. The finest lands or raised dots. are freed from all mechanical con-' tact and are subjected only to the acid spray, the pressure air barrier, and the water spray. Thus the improved method of the present invention across the pressure air barrier located intermeaccomplishes the highly desirable function of The contact between etching fluid, a water spray, and an air blast for doctoring oil the excess water, said steps being repeated until the surface of the cylinder is com pletely etched.

2. In an etching machine, means providing an etching zone, means defining a first air doctor zone, means defining a washing zone, means delining a second air doctor zone, and a source of pressure air connected to said first and said second air doctor zones, said etching zone being located intermediate said air doctor zones and said washing zone being located adjacent said second air doctor zone, and means for repeatedly passing the surface to be etched consecutively through said zones in a manner such that said surface is successively and repeatedly exposed to said first air doctor zone, said etching zone, said second air doctor zone, and said washing zone.

3. In combination in an etching machine for etching the peripheral surface of aprinting cylinder, means for supporting the cylinder to be etched for rotation about a generally horizontal axis, a trough having a narrow, longitudinally extending, open mouth whose major axis is generally parallel with the axis of rotation of the cylinder to be etched, the trough and cylinder being so supported and related that the peripheral surface of the cylinder although out of contact withthe trough provides an effective closure for the open mouth, means for projecting etching liquid in the trough against that portion'of the peripheral surface of the cylinder which closes the mouth, means for rotating the cylinder to 'cause successive portions of the peripheral surface of the cylinder to move out of register with the open mouth, means for projecting water against the peripheral surface of the cylinder outside of the trough after it has moved out of register with the mouth, and means for discharging an air jet against the peripheral surface of the cylinder.

4. In combination in an etching machine for etching the peripheral surface of a printing cylinder, means for supporting the cylinder to'be etched for rotation about a generally horizontal axis, a trough having a. narrow, longitudinally extending, open mouth whose major axis is generally parallel with the axisof rotation of the cylinder to be etched, the trough and cylinder being so supported and related that the peripheral surface of the cylinder although out of contact with the trough provides an effective closure for the open mouth, means for projecting etching liquid in the trough against that portion of the peripheral surface of the cylinder which closes the mouth, means for rotating the cylinder to cause successive portions of the peripheral surface of the cylinder to move out of register with the open mouth, means for projecting water against the peripheral surface of the cylinder outside of the trough after it has moved out of register with the mouth, and means for projecting an air'jet against the peripheral surface of the cylinder, the air-jet-projecting-means being located between the mouth of the trough and the water-projecting-means.

5. In combination in an etchingmachine for etching the peripheral surface of a printing cylinder, means for supporting the cylinder to be etched for rotation about a generally horizontal axis, a trough having a narrow, longitudinally extendin open mouth whose major axis is generally parallel with the axis of rotation of the cylinder to be etched, the trough and cylinder being so supported and related that the peripheral surface of the cylinder although out of contact with the trough provides an effective closure for the open mouth, means for projecting etching liquid in the trough against that portion of the peripheral surface of the cylinder which closes the mouth, means for rotating the cylinder to cansesuccessive portions of the peripheral surface of the cylinder to move out of register with the open mouth, means for projecting air jets against the peripheral" surface of the cylinder, the air-jet-projecting-means being positioned to bound the sides of the mouth which are parallel to the major axis thereof, and means for projecting water against the peripheral surface of the cylinder outside of the trough'inimediately after it has moved out of register with the mouth and the air-jet-projecting-means which bounds the side of the mouth.

6. In combination in an etching machine for etching the peripheral surface of a printing cylinder, means for supporting the'cylinder to be etched for rotation about a generally horizontal axis, a trough having a narrow, longitudinally extending open mouth whose major axis is generally parallel with the axis of rotation of the cylinder to be etched, the trough and cylinder being so supported and related that the peripheral surface of the cylinder although out of contact with the trough provides an effective closure for the open mouth, means for projecting etching liquid in the trough against that portion of the peripheral surface of the cylinder which closes the mouth, means disposed along each of the sides of the trough which are parallel to the major axis thereof, for projecting an elongated air jet against the peripheral surface of the cylinder, means for rotating the cylinder to cause successive portions of the peripheral surface of the cylinder to move out of register with the open mouth, and across the air-jet-projecting-means, and means for .continuously projecting water against the peripheral surface of the cylinder along its entire length after it has moved out of register with the mouth.

CHARLES L. HENDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 590,966 Cornwall Oct. 5, 1897 1,166,378 Levy Dec. 28, 1915 2,293,201 Gaebel Aug. 18,1942 2,360,676 Henderson Oct. 17, 1944 FOREIGN PATENTS Number Country Date 229,956 Great Britain Mar. 5, 1925 

